/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * <p/>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p/>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.fs.obs;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;

import com.google.common.util.concurrent.ListenableFuture;

import org.apache.hadoop.util.StopWatch;
import org.junit.AfterClass;
import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.Timeout;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.TimeUnit;

/**
 * Basic test for OBS's blocking executor service.
 */
public class ITestOBSBlockingThreadPoolExecutorService {

    private static final Logger LOG = LoggerFactory.getLogger(
        BlockingThreadPoolExecutorService.class);

    private static final int NUM_ACTIVE_TASKS = 4;

    private static final int NUM_WAITING_TASKS = 2;

    private static final int TASK_SLEEP_MSEC = 100;

    private static final int SHUTDOWN_WAIT_MSEC = 200;

    private static final int SHUTDOWN_WAIT_TRIES = 5;

    private static final int BLOCKING_THRESHOLD_MSEC = 50;

    private static final Integer SOME_VALUE = 1337;

    private static BlockingThreadPoolExecutorService tpe;

    @Rule
    public OBSTestRule testRule = new OBSTestRule();

    @Rule
    public Timeout testTimeout = new Timeout(60 * 1000);

    @AfterClass
    public static void afterClass() throws Exception {
        ensureDestroyed();
    }

    /**
     * Basic test of running one trivial task.
     */
    @Test
    // 线程池可正常提交Callable任务
    public void testSubmitCallable() throws Exception {
        ensureCreated();
        ListenableFuture<Integer> f = tpe.submit(callableSleeper);
        Integer v = f.get();
        assertEquals(SOME_VALUE, v);
    }

    /**
     * More involved test, including detecting blocking when at capacity.
     */
    @Test
    // 线程池可正常提交Runnable任务
    public void testSubmitRunnable() throws Exception {
        ensureCreated();
        verifyQueueSize(tpe, NUM_ACTIVE_TASKS + NUM_WAITING_TASKS);
    }

    /**
     * Verify the size of the executor's queue, by verifying that the first
     * submission to block is {@code expectedQueueSize + 1}.
     *
     * @param executorService   executor service to test
     * @param expectedQueueSize size of queue
     */
    protected void verifyQueueSize(ExecutorService executorService,
        int expectedQueueSize) {
        StopWatch stopWatch = new StopWatch().start();
        for (int i = 0; i < expectedQueueSize; i++) {
            executorService.submit(sleeper);
            assertDidntBlock(stopWatch);
        }
        executorService.submit(sleeper);
        assertDidBlock(stopWatch);
    }

    @Test
    // 线程池可正常shutdown
    public void testShutdown() throws Exception {
        // Cover create / destroy, regardless of when this test case runs
        ensureCreated();
        ensureDestroyed();

        // Cover create, execute, destroy, regardless of when test case runs
        ensureCreated();
        testSubmitRunnable();
        ensureDestroyed();
    }

    @Test
    // 线程池任务可排队
    public void testChainedQueue() throws Throwable {
        ensureCreated();
        int size = 2;
        ExecutorService wrapper = new SemaphoredDelegatingExecutor(tpe,
            size, true);
        verifyQueueSize(wrapper, size);
    }

    // Helper functions, etc.

    private void assertDidntBlock(StopWatch sw) {
        try {
            assertFalse("Non-blocking call took too long.",
                sw.now(TimeUnit.MILLISECONDS) > BLOCKING_THRESHOLD_MSEC);
        } finally {
            sw.reset().start();
        }
    }

    private void assertDidBlock(StopWatch sw) {
        try {
            if (sw.now(TimeUnit.MILLISECONDS) < BLOCKING_THRESHOLD_MSEC) {
                throw new RuntimeException("Blocking call returned too fast.");
            }
        } finally {
            sw.reset().start();
        }
    }

    private Runnable sleeper = new Runnable() {
        @Override
        public void run() {
            String name = Thread.currentThread().getName();
            try {
                Thread.sleep(TASK_SLEEP_MSEC);
            } catch (InterruptedException e) {
                LOG.info("Thread {} interrupted.", name);
                Thread.currentThread().interrupt();
            }
        }
    };

    private Callable<Integer> callableSleeper = new Callable<Integer>() {
        @Override
        public Integer call() throws Exception {
            sleeper.run();
            return SOME_VALUE;
        }
    };

    /**
     * Helper function to create thread pool under test.
     */
    private synchronized static void ensureCreated() throws Exception {
        if (tpe == null) {
            LOG.debug("Creating thread pool");
            tpe = BlockingThreadPoolExecutorService.newInstance(
                NUM_ACTIVE_TASKS, NUM_WAITING_TASKS,
                1, "btpetest");
        }
    }

    /**
     * Helper function to terminate thread pool under test, asserting that
     * shutdown -> terminate works as expected.
     */
    private static void ensureDestroyed() throws Exception {
        if (tpe == null) {
            return;
        }
        int shutdownTries = SHUTDOWN_WAIT_TRIES;

        tpe.shutdown();
        if (!tpe.isShutdown()) {
            throw new RuntimeException("Shutdown had no effect.");
        }

        while (!tpe.awaitTermination(SHUTDOWN_WAIT_MSEC,
            TimeUnit.MILLISECONDS)) {
            LOG.info("Waiting for thread pool shutdown.");
            if (shutdownTries-- <= 0) {
                LOG.error("Failed to terminate thread pool gracefully.");
                break;
            }
        }
        if (!tpe.isTerminated()) {
            tpe.shutdownNow();
            if (!tpe.awaitTermination(SHUTDOWN_WAIT_MSEC,
                TimeUnit.MILLISECONDS)) {
                throw new RuntimeException(
                    "Failed to terminate thread pool in timely manner.");
            }
        }
        tpe = null;
    }
}
